<template>
  <div>
  <router-link class="header-abs" tag="div" to="/" v-show="showAbs">
    <div class="iconfont header-abs-back">&#xe624;</div>
      </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
      <router-link to="/">
      <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
</div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data() {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {
          opacity
        }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  mounted () {//activated
    window.addEventListener('scroll', this.handleScroll)
  },
  destroyed () {//deactivated  ...这两个生命周期钩子函数不能用了，因为我在keep-alive中加入了exclude屏蔽了该组件，所以没有这两个钩子函数
    window.addEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .header-abs
    position absolute
    left .2rem
    top .2rem
    width .8rem
    height .8rem
    border-radius .4rem
    background-color rgba(0,0,0,.8)
    text-align center
    line-height .8rem
    .header-abs-back
      color #fff
      font-size .4rem
  .header-fixed
    z-index 2
    position fixed
    top 0
    left 0
    right 0
    height .86rem
    line-height .86rem
    text-align center
    color white
    background $bgColor
    font-size .32rem
    .header-fixed-back
      position absolute
      top:0
      left:0
      width .64rem
      text-align center
      font-size .4rem
      color white
</style>
